首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   248篇
  免费   0篇
安全科学   5篇
废物处理   5篇
环保管理   37篇
综合类   14篇
基础理论   107篇
污染及防治   53篇
评价与监测   19篇
社会与环境   8篇
  2022年   1篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2017年   2篇
  2016年   5篇
  2015年   8篇
  2014年   10篇
  2013年   7篇
  2012年   9篇
  2011年   12篇
  2010年   7篇
  2009年   2篇
  2008年   9篇
  2007年   10篇
  2006年   12篇
  2005年   7篇
  2004年   4篇
  2003年   6篇
  2002年   9篇
  2001年   9篇
  2000年   13篇
  1999年   13篇
  1998年   4篇
  1997年   5篇
  1996年   2篇
  1995年   6篇
  1994年   5篇
  1993年   6篇
  1992年   10篇
  1991年   6篇
  1990年   7篇
  1989年   5篇
  1988年   7篇
  1987年   4篇
  1986年   2篇
  1985年   4篇
  1984年   1篇
  1983年   2篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1975年   3篇
  1974年   1篇
  1969年   1篇
  1959年   1篇
  1956年   1篇
排序方式: 共有248条查询结果,搜索用时 46 毫秒
231.
This paper is concerned with the effects of advanced manufacturing technology on shopfloor operator jobs and work attitudes. A strong line of argument from labour process theory suggests that such technology will simplify and deskill jobs, and reduce the quality or working life. This proposition was explored within a large electronics company which assembles computer boards, where two different applications of information technology have been experienced. These were compared with two traditional manual assembly jobs. Assessment of job content, perceived job characteristics and operator work attitudes, showed no uniform deskilling effects of advanced manufacturing technologies. Much larger differences existed both between the different new technology applications and between the traditional jobs. This demonstrates that choice of technology is important to skill use and employees' attitudes, as are the choices for the organization of work around it. These are not uniform processes even within a single organization. Experience of operating advanced manufacturing technology was also accompanied by more positive views concerning its impact on the shopfloor.  相似文献   
232.
The Oslo and Paris Commission (OSPAR) Guidelines for monitoring the biological effects of tributyltin compounds (TBT) were evaluated using data collected for preparation of a Celtic Seas Quality Status Report. Two types of survey were undertaken: broad scale, to determine wide impacts in coastal waters; and localised, around representative harbours to establish ranges of effect from recognised input points. This evaluation indicates that results from the broad scale surveys can be used to compare different areas of coastline. Nucella is widespread away from point sources although many individuals show some degree of imposex. Populations are generally not at risk. The localised surveys indicate that, in certain situations, the monitoring objectives can be met in the OSPAR Guidelines (subject to minor amendment). Criteria are identified for the selection of point sources suitable for monitoring under OSPAR Guidelines.  相似文献   
233.
When quantifying imposex in Nucella lapillus, two indices are used: the Vas Deferens Sequence Index (VDSI) and the Relative Penis Size Index (RPSI). Freezing and thawing increase the length of the penis in both male and female Nucella lapillus. In the population studied, this had no significant effect on the RPSI, but was potentially an important source of additional variance in the estimation of the mean penis length.  相似文献   
234.
In order to examine the effect of light level on the storage lipids of the symbiotic sea anemoneAnemonia virudis (Forskäl), anemones were exposed to three experimental light regimes of 10, 100 and 300 E m-2s-1. Anemones were fed once a week. After 30 d there were no significant differences in the total lipid levels between anemones at any of the light intensities. However, after 60 d lipids had increased in proportion to light level in both the animal-tissue and zooxanthellae compartments. The higher levels of total lipid were in part due to increases in storage lipid (wax esters and triglycerides). Wax ester levels increased in the animal tissues but remained constant in the zooxanthellae, whereas triglycerides increased in both compartments. In contrast to fed anemones, starved anemones which were maintained at 300 E m-2s-1 for 30 or 60 d did not show a statistically significant change in lipid levels at 60 d, although a slight increase in the lipid level was observed. However, there was a significant increase in the storage lipids, which suggested that the non-storage phospholipids and structural lipids had declined as a result of cellular catabolism. The composition of the wax esters and triglycerides of both fed and starved anemones was analysed and compositional changes were observed at higher light intensities.  相似文献   
235.
A field experiment to investigate the formation of nitrate as an airstream passes through a hill cap cloud has been performed at the UMIST field station on Great Dun Fell. It has been shown that the aerosol nitrate concentration increased by about 0.5 microg m(-3) as the airstream passed through the cloud during the night. At sunrise the nitrate production disappeared. It is suggested that the most likely mechanism for this nitrate production was due to the solution of N2O5 and NO3 formed from the reaction of NO2 with O3. These higher oxides build up overnight in the absence of short wave radiation to photolyse them. Other possible mechanisms of nitrate production are also discussed.  相似文献   
236.
Evidence is accumulating that the continued provision of essential ecosystem services is vulnerable to land-use change. Yet, we lack a strong scientific basis for this vulnerability as the processes that drive ecosystem-service delivery often remain unclear. In this paper, we use plant traits to assess ecosystem-service sensitivity to land-use change in subalpine grasslands. We use a trait-based plant classification (plant functional types, PFTs) in a landscape modeling platform to model community dynamics under contrasting but internally consistent land-use change scenarios. We then use predictive models of relevant ecosystem attributes, based on quantitative plant traits, to make projections of ecosystem-service delivery. We show that plant traits and PFTs are effective predictors of relevant ecosystem attributes for a range of ecosystem services including provisioning (fodder), cultural (land stewardship), regulating (landslide and avalanche risk), and supporting services (plant diversity). By analyzing the relative effects of the physical environment and land use on relevant ecosystem attributes, we also show that these ecosystem services are most sensitive to changes in grassland management, supporting current agri-environmental policies aimed at maintaining mowing of subalpine grasslands in Europe.  相似文献   
237.
Poverty and corruption compromise tropical forest reserves.   总被引:1,自引:0,他引:1  
We used the global fire detection record provided by the satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) to determine the number of fires detected inside 823 tropical and subtropical moist forest reserves and for contiguous buffer areas 5, 10, and 15 km wide. The ratio of fire detection densities (detections per square kilometer) inside reserves to their contiguous buffer areas provided an index of reserve effectiveness. Fire detection density was significantly lower inside reserves than in paired, contiguous buffer areas but varied by five orders of magnitude among reserves. The buffer: reserve detection ratio varied by up to four orders of magnitude among reserves within a single country, and median values varied by three orders of magnitude among countries. Reserves tended to be least effective at reducing fire frequency in many poorer countries and in countries beset by corruption. Countries with the most successful reserves include Costa Rica, Jamaica, Malaysia, and Taiwan and the Indonesian island of Java. Countries with the most problematic reserves include Cambodia, Guatemala, Paraguay, and Sierra Leone and the Indonesian portion of Borneo. We provide fire detection density for 3964 tropical and subtropical reserves and their buffer areas in the hope that these data will expedite further analyses that might lead to improved management of tropical reserves.  相似文献   
238.
Key goals of conservation are to protect both species and the functional and genetic diversity they represent. A strictly species-based approach may underrepresent rare, threatened, or genetically distinct species and overrepresent widespread species. Although reserves are created for a number of reasons, including economic, cultural, and ecological reasons, their efficacy has been measured primarily in terms of how well species richness is protected, and it is useful to compare how well they protect other measures of diversity. We used Proteaceae species-occurrence data in the Cape Floristic Region of South Africa to illustrate differences in the spatial distribution of species and evolutionary diversity estimated from a new maximum-likelihood molecular phylogeny. We calculated species richness, phylogenetic diversity (i.e., summed phylogenetic branch lengths in a site), and a site-aggregated measure of biogeographically weighted evolutionary distinctiveness (i.e., an abundance weighted measure that captures the unique proportion of the phylogenetic tree a species represents) for sites throughout the Cape Floristic Region. Species richness and phylogenetic diversity values were highly correlated for sites in the region, but species richness was concentrated at a few sites that underrepresented the much more spatially extensive distribution of phylogenetic diversity. Biogeographically weighted evolutionary diversity produced a scheme of prioritization distinct from the other 2 metrics and highlighted southern sites as conservation priorities. In these sites, the high values of biogeographically weighted evolutionary distinctiveness were the result of a nonrandom relation between evolutionary distinctiveness and geographical rarity, where rare species also tended to have high levels of evolutionary distinctiveness. Such distinct and rare species are of particular concern, but are not captured by conservation schemes that focus on species richness or phylogenetic diversity alone.  相似文献   
239.
Catastrophic die-offs can have important consequences for vertebrate population growth and biodiversity, but catastrophic risks are not commonly incorporated into endangered-species recovery planning. Natural (e.g., landslides, floods) and anthropogenic (e.g., toxic leaks and spills) catastrophes pose a challenge for evolutionarily significant units (ESUs) of Pacific salmon listed under the Endangered Species Act and teetering at precariously low population levels. To spread risks among Puget Sound chinook salmon populations, recovery strategies for ESU-wide viability recommend at least two viable populations of historical life-history types in each of five geographic regions. We explored the likelihood of Puget Sound chinook salmon ESU persistence by examining spatial patterns of catastrophic risk and testing ESU viability recommendations for 22 populations of the threatened Puget Sound chinook salmon ESU. We combined geospatial information about catastrophic risks and chinook salmon distribution in Puget Sound watersheds to categorize relative catastrophic risks for each population. We then analyzed similarities in risk scores among regions and compared risk distributions among strategies: (1) population groups selected using the ESU viability recommendations of having populations spread out geographically and including historical life-history diversity, and (2) population groups selected at random. Risks from individual catastrophes varied among populations, but overall risk from catastrophes was similar within geographic regions. Recovery strategies that called for two viable populations in each of five geographic regions had lower risk than random strategies; strategies that included life-history diversity had even lower risks. Geographically distributed populations have varying catastrophic-risks profiles, thus identifying and reinforcing the spatial and life-history diversity critical for populations to respond to environmental change or needed to rescue severely depleted or extirpated populations. Recovery planning can promote viability of Pacific salmon ESUs across the landscape by incorporating catastrophic risk assessments.  相似文献   
240.
Assessment of river 'health' using biological methods, particularly those based on macro-invertebrates, is now commonplace in most developed countries. However, this is not the case in most developing countries, where physical and chemical methods are used to assess water quality, with very little use of biological assessment methods. This paper reports on a project that aimed to assess the possible introduction of biological assessment of river condition using the Australian River Assessment System (AUSRIVAS) into Indonesia. The paper addresses three components of the project: (1) science--does the bioassessment method work in this tropical region? (2) resources--are they adequate and if not what additional resources are needed? (3) politics--what needs to be done to convince the agencies (both central and provincial) to take up such a new philosophy and approach? A pilot study was run in the upper Brantas River, East Java. A total of 66 reference sites and 15 test sites were sampled and the macro-invertebrates collected were identified to family level. A rigorous quality-control protocol was introduced to ensure the data were reliable and reproducible. The macro-invertebrate data were used to develop a predictive model of the AUSRIVAS type for the upper Brantas River, and the model was then used to assess the 'health' of sites that were presumed to be damaged in this section of the river. A number of difficulties were experienced during the study, including: locating reference sites sufficiently unmodified by humans; lack of skills to identify animals collected; and a paucity of facilities required for aquatic macro-invertebrate identification (e.g. identification keys and good quality binocular microscopes). For resources, the major constraint to the introduction of a bioassessment capability in Indonesia is the lack of personnel trained in the bioassessment techniques. An 'on-the-job' training approach was adopted, largely because of the specialist nature of this work. Six Indonesians were trained and will now become the 'trainers' of further Indonesian scientists (we have called this process 'training-the-trainers'). For politics, it was hoped that the AUSRIVAS method would be suitable for introduction into the Indonesian national Clean River Program. A strategy was developed and implemented to ensure the method and its outputs were accepted technically by the Indonesian scientific community, and also by the resource managers and relevant government officials. Experience shows that if the latter do not see how the bioassessment information will be used for management purposes they will not accept the method even if it is scientifically sound.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号